Parking Structure Memory-Module Tester that Moves Test Motherboards Along a Highway for Remote Loading/Unloading

ABSTRACT

A parking-structure test system has motherboards that test memory modules. The motherboards are not stationary but are placed inside movable trays that move along conveyors. An unloader removes tested memory modules from test sockets on the motherboards, and a loader inserts untested memory modules into the motherboards using a robotic arm. A conveyor carries the motherboards from the loader to a parking and testing structure. An elevator raises or lowers the motherboards to different parking levels in the parking and testing structure. The motherboards move from the elevator to test stations on the parking level. A retractable connector from the test station makes contact with a motherboard connector to power up the motherboard, which then tests the memory modules. Test results are communicated from the test station to a host controller, which instructs the loader-unloader to sort the tested memory modules once the motherboard returns via the elevator and conveyors.

RELATED APPLICATION

This application is a continuation of U.S. Ser. No. 12/392,401 filedFeb. 25, 2009, now U.S. Pat. No. ______.

FIELD OF THE INVENTION

This invention relates to electronic-test systems, and more particularlyto test system with movable test motherboards that are moved from aloader to a vertical parking structure for testing memory modulesincluding SIMMs and DIMMs.

BACKGROUND OF THE INVENTION

Memory is a fundamental part of many digital electronic systems. Avariety of electronic systems including personal computers (PCs) useDRAM memory chips mounted on small, removable memory modules. Oldersingle-inline memory modules (SIMMs) have been replaced with dual-inlinememory modules (DIMMs), and 184-pin RIMMs (Rambus inline memory modules)and 184-pin DDR (double data rate) DIMMs. New kinds of memory modulescontinue to be introduced.

The memory-module industry is quite cost sensitive. Testing costs aresignificant, especially for higher-density modules. Specialized,high-speed electronic test equipment is expensive, and the greaternumber of memory cells on high-speed memory modules increases the timespent on the tester, increasing test costs.

Handlers for integrated circuits (ICs) have been used for many years inthe semiconductor industry. Handlers accept a stack of IC chips that arefed, one at a time, to the tester. The tested IC is then sorted into a“bin” for IC chips that have passed or failed the test. Handlers havealso been developed for memory modules.

Rather than use an expensive general-purpose I.C. tester, inexpensivetesters based on PC motherboards have been developed. Thesemotherboard-based testers cost only about $10K while replacing aquarter-million-dollar I.C. tester. The memory module to be tested isinserted into a test socket on a test adapter board (daughter card)mounted on the back-side of the motherboard. Special handlers can beused for module insertion.

Elevated-temperature testing is often desired to more thoroughly screenfor defects. Hot air can be blown onto the memory module being tested.Ideally, the motherboard itself is cooled while the memory module undertest is heated. See U.S. Pat. No. 6,357,023 for “Connector Assembly forTesting Memory Modules from the Solder-Side of a PC Motherboard withForced Hot Air”.

FIG. 1 highlights a motherboard-based memory tester. A conventional PCmotherboard is mounted upside-down within chassis 60. Rather thanconnect motherboard substrate 30 directly to chassis 60, as in aconventional PC, motherboard substrate 30 is mounted to metal plate 64by standoffs or spacers 61. Motherboard substrate 30 is not mounteddirectly to chassis 60 in this embodiment, although it could be in someembodiments. Screws, bolts, or clamps (not shown) can be used to securemetal plate 64 to chassis 60.

Test adapter board 50 is mounted to well 66, while well 66 is mounted tometal plate 64. Test socket 51 is mounted to test adapter board 50,while pins 52 provide electrical connection from test socket 51 tomotherboard substrate 30. The memory module 18 being tested is insertedinto test socket 51. Test adaptor board 50 provides electricalconnection from the module-under-test (MUT) in the SIMM/DIMM test socket51 to the leads for the removed SIMM socket on the PC motherboard.

Motherboard substrate 30 has components 42, 44 (I.C. chips, sockets,capacitors, etc.) mounted on component-side 32 of substrate 30. Memorymodules 36 are SIMM or DIMM modules that fit into SIMM/DIMM sockets 38.SIMM/DIMM sockets 38 (hereinafter SIMM sockets 38) have metal pins thatfit through holes in substrate 30. Expansion cards 46 are plugged intoexpansion sockets that are also mounted onto component-side 32 ofsubstrate 30. Cables 48 and expansion cards 46 are bulky but do notinterfere with a robotic arm inserting memory module 18 into test socket51 since cables 48 and expansion cards 46 are mounted below substrate30, while test socket 51 is mounted above substrate 30. Cables 48 andexpansion cards 46 are kept out of the way inside chassis 60.

Test adapter board 50 is a small circuit board that allows an automatedhandler, a person, or a robotic arm easy access to SIMM/DIMM test socket51 that is mounted on test adaptor board 50. Test socket 51 on onesurface of test adapter board 50 mates with connectors on SIMM/DIMMmemory module 18, the module-under test. The other surface of adaptorboard 50 has adapter pins 52 inserted in holes to make electricalcontact. These adaptor pins are soldered into through-holes in adaptorboard 50 and in substrate 30. Adapter pins 52 are arranged to have thesame arrangement and spacing as the substrate-mounting pins for SIMMsockets 38. One or more of SIMM sockets 38 has been removed from thecomponent side of the PC motherboard, leaving the through-holes. Adapterpins 52 are then fitted through the exposed through holes for theremoved SIMM socket. Rather than push the pins through fromcomponent-side 32, adapter pins 52 are pushed through from solder-side34 to component-side 32.

Cooling fan 71 is provided in chassis 60 to cool motherboard substrate30 and its components 42, 44 and expansion cards 46. Even air at roomtemperature can be effective at cooling the motherboard if a sufficientvolume of air is blown past the motherboard's components. Componentssuch as integrated circuits heat up during operation and benefit fromsuch cooling. Of course, reduced-temperature air could also be blowninto chassis 60, such as air from outside a building in a cold climate.

Since metal plate 64 separates motherboard substrate 30 from testadapter board 50, the cooling air from cooling fan 71 is separated fromany heated air blown against memory module 18 under test. Test adapterboard 50 is mounted within well 66 and forms a sufficient seal toprevent the cooling air within chassis 60 from cooling memory module 18being heated and tested.

FIG. 2 is an overhead diagram looking down on a multi-motherboard teststation with overhead rails for an x-y-z robotic handler. See “AutomatedMulti-PC-Motherboard Memory-Module Test System with Robotic Handler andIn-Transit Visual Inspection”, U.S. Pat. No. 6,415,397. Operator 100 cansit in front of the test station, controlling operation with atouch-screen or keyboard. Trays of untested memory modules can include abarcode that is scanned in to main system interface 65 by operator 100before the tray is put into input stacker 63. Robotic handler 80 thenpicks untested modules that are moved over to input tray 62 by stacker63. The modules are first inserted into leakage tester 82. Modules thatpass are then moved by robotic handler 80 to the test socket on the testadaptor board on the solder-side of one of motherboard substrates 30 fortesting.

Modules that fail the motherboard or leakage test are placed on repairtray 76 by robotic handler 80. Modules passing the motherboard test arepulled from the test socket by robotic handler 80 and moved in front ofcameras 75 for visual inspection. Modules failing visual inspection aredropped into VI tray 78. Passing modules are placed on output tray 72and full trays are moved by stacker 73 to the front of the test stationwhere operator 100 can remove them.

Each of the motherboards fits into a well in the frame of the teststation. The test station has a surface at about bench-top levelcomposed of the exposed solder sides of the motherboards in the wells inthe frame. Robotic handler 80 rides on rails 92, 94 mounted above thelevel of the motherboards, such as above the head of a seated operator100. Operator 100 also replaces repair tray 76 and VI tray 78 with emptytrays when full.

Fixed rails 92, 94 in the x direction allow movable y-rail 96 to travelin the x direction. Robot arm assembly 98 then travels in the ydirection along y-rail 96 until robot arm assembly 98 is directly overthe desired position, such as a test socket on an adaptor board, or aninput or output tray. An elevator arm on robot arm assembly 98 thenmoves up and down, pulling out (up) a module or inserting a module into(down) a test socket or tray. Robot arm assembly 98 can also rotate orspin the module into the desired position.

While such motherboard-based testers are useful, higher-density testersare desired that have more motherboards in a smaller amount of floorarea in a manufacturing facility. While these test systems use low-costmotherboards, the motherboards are fixed in location and are stationary.The robotic arm of robotic handler 80 of FIG. 2 must have a long traveldistance to reach all motherboards on the test system of FIG. 2. Thisincreases the cost of the robotic handler. The fixed number ofmotherboards 30 that can be reached by robotic handler 80 limits thenumber of memory modules that can be tested at one time by the testsystem.

What is desired is a larger test system. A test system that tests memorymodules on motherboards is desirable to reduce cost. It is furtherdesired to test memory modules using more motherboards than can bereached by the robotic arm.

It is desired to move motherboards using a conveyor and elevator systemso that motherboards may perform testing at a structure located awayfrom robotic handlers, thus increasing the number of motherboards thatmay be serviced by a robotic handler. It is desired to load and unloadmemory modules from motherboards when these motherboards are moved nearthe robotic handler, but perform testing when these motherboards arelocated away from the robotic handler. Thus a smaller robotic handlermay be used with a large number of movable motherboards.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 highlights a motherboard-based memory tester.

FIG. 2 is an overhead diagram looking down on a multi-motherboard teststation with overhead rails for an x-y-z robotic handler.

FIG. 3 is a diagram of a test system that moves motherboards from aloader-unloader to parking and testing structures where testing isperformed.

FIG. 4 is a side view of a parking and testing structure.

FIGS. 5A-E are side views of raising a motherboard to a parking levelfor testing in a parking and testing structure.

FIGS. 6A-C are top views of testing a motherboard in a movable tray at aparking level in the parking and testing structure.

FIG. 7 shows the loader-unloader in more detail.

FIG. 8 shows an alternate embodiment of the parking and testingstructure.

FIG. 9 is an elevator that raises and lowers movable motherboard-basedtesters.

FIG. 10 is a diagram of a Ferris-wheel type of elevator.

DETAILED DESCRIPTION

The present invention relates to an improvement in motherboard-basedtest systems. The following description is presented to enable one ofordinary skill in the art to make and use the invention as provided inthe context of a particular application and its requirements. Variousmodifications to the preferred embodiment will be apparent to those withskill in the art, and the general principles defined herein may beapplied to other embodiments. Therefore, the present invention is notintended to be limited to the particular embodiments shown anddescribed, but is to be accorded the widest scope consistent with theprinciples and novel features herein disclosed.

The inventor has realized that robotic test systems are limited by thenumber of motherboards that can be reached by a robotic arm. The highcost of the robotic arm that inserts and removes memory modules from themotherboards increases tester and testing costs.

The inventor has further realized that the motherboards do not have tobe within reach of the robotic arm while the motherboards are testingthe memory modules. Some kinds of testing may require long periods oftime, such as characterization and quality testing. During these longtest periods, the motherboard may be moved away from the robotic arm,allowing other motherboards to be moved within range of the robotic arm.Thus one robotic arm may service many more motherboards than the fewmotherboards that would fit within the reach of the robotic arm. Testingthroughput may be dramatically increased without increasing the cost ofthe robotic arm handler.

Conveyors may be used to move motherboards away from the robotic arm toa parking structure. The parking structure accepts and powers up themotherboards to perform testing. After testing is complete, themotherboards may be moved from the parking structure by the conveyorback to the robotic arm so that the tested memory modules may be removedand new untested memory modules inserted to begin the cycle anew.

FIG. 3 is a diagram of a test system that moves motherboards from aloader-unloader to parking and testing structures where testing isperformed.

Untested memory modules from an assembly line are received in inputtrays 346 and are picked up by loader 348, which may use a robotic arm.The memory modules are tested in a simple D.C. tester for major failuressuch as shorts, and a serial-presence-detect electrically-erasableprogrammable read-only memory (SPD-EEPROM) on each memory module isprogrammed. The robotic arm of loader 348 then inserts passing memorymodules into test sockets on motherboards that are on movable tray 10currently near loader 348.

The motherboards in movable trays 10 are each a modified personalcomputer (PC) motherboard with a microprocessor and other chips that usememory modules as the main memory of the motherboard. However, ratherthan having standard memory modules sockets, these motherboards havetest sockets, and may have a small test adaptor board mounted to themotherboard, with the test sockets mounted to the test adaptor board asshown in FIG. 1. The robotic arm of loader 348 loads or inserts memorymodules into the test sockets, and these memory modules in the testsockets act as the module-under-test (MUT).

Movable trays 10 have been placed on highway conveyor 330, which may beone or more conveyor belts or rollers on one or more levels, or someother conveyor system. Each movable tray 10 can hold one or moremotherboards, such as two motherboards. Movable trays 10 with loadedmotherboards are moved along as highway conveyor 330 moves to the rightuntil movable tray 10 reaches parking and testing structures 350, 352.

Parking and testing structures 350, 352 each have multiple levels and anelevator. Motherboards on movable tray 10 are raised and lowered by theelevator and “parked” on an empty level. When a motherboard is parked ona level, the motherboard is plugged into power, which activates themotherboard to test the memory modules that were inserted into testsockets on the motherboard. Once testing is complete, the motherboardwith its tested memory modules is removed from the parking level by theelevator and returned to the level of highway conveyor 330.

Movable trays 10 with tested memory modules are removed from parking andtesting structures 350, 352 and moved along to the left by highwayconveyor 330. Highway conveyor 330 may have a second level that moves tothe left, or may have parallel tracks that move in a loop, or mayreverse direction. When the tested motherboards in movable tray 10 reachthe unloading station at the far left, unloader 344 uses a robotic armto remove the tested memory modules from the test sockets on themotherboards in movable tray 10. The tested memory modules are sortedinto failing and passing trays, with passing memory modules placed onoutput tray 342. The passing memory modules on output tray 342 may besent to the shipping department.

A host controller or computer at unloader 344 can receive test resultsfrom another computer that controls testing at parking and testingstructures 350, 352. The test results are used to sort the tested memorymodules.

The movable tray 10 holding motherboards with empty test sockets ismoved by highway conveyor 330 from unloader 344 to loader 348. Loader348 then inserts new memory modules into the empty test sockets on themotherboards. The test cycle can then begin again.

FIG. 4 is a side view of a parking and testing structure. Elevator 270raises and lowers motherboard substrate 30 on movable tray 10 onelevator table 276.

Untested memory modules in motherboard substrate 30 are moved by movabletray 10 from input highway 332 to elevator 270, which lifts movable tray10 and motherboard substrate 30 to one of the many parking levels inparking and testing structure 350. Each parking level has a parkingconveyor 280, which holds movable tray 10. At the selected level,elevator 270 pushes movable tray 10 off of elevator table 276 and ontoparking conveyor 280.

The memory modules inserted into motherboard substrates 30 are tested attest stations 20 located at the end of parking conveyors 280. Oncetesting is completed, parking conveyor 280 pushes movable tray 10 andmotherboard substrate 30 onto elevator table 276 when elevator 270 isaligned with that parking level. Elevator 270 returns to the level ofoutput highway 334, and elevator 270 forces movable tray 10 off ofelevator table 276 and onto output highway 334. Output highway 334 thenmoves movable tray 10 to unloader 344 of FIG. 3.

Input highway 332 and output highway 334 can be part of highway conveyor330 of FIG. 3. For example, input highway 332 and output highway 334 canbe conveyors that form a continuous loop with unloader 344 and loader348. When a movable tray reaches the right end of output highway 334,the movable tray is turned onto or lifted up to input highway 332 andcontinues to move to the right. When a movable tray reaches the rightend of input highway 332, the movable tray is turned onto or droppeddown by elevator 270 to output highway 334 and continues to move to theright.

FIGS. 5A-E are side views of raising a motherboard to a parking levelfor testing in a parking and testing structure. In FIG. 5A, two parkinglevels 28 are shown, but many parking levels may be present in a parkingand testing structure 350. Each parking level 28 is a parking conveyorthat can hold movable tray 10. Movable tray 10 has one or moremotherboard substrate 30. Motherboard substrate 30 is a PC motherboardthat uses memory module 18 inserted into test socket 51 as the mainmemory that is accessed by a microprocessor and other components 42, 44.

Each test station 20 has a retractable connector 14 that mates withmotherboard connector 12 on motherboard substrate 30 to apply power tothe motherboard. Test results generated by motherboard substrate 30testing memory modules 18 are sent through connectors 12, 14 to teststation 20, and then communicated over Ethernet 24 or another networkbus to a host controller.

In FIG. 5A, movable tray 10 on the lower level is being moved fromhighway conveyor 330 toward elevator table 276 in elevator 270 of FIG.4. Elevator table 276 is aligned with highway conveyor 330. In FIG. 5B,movable tray 10 is fully pushed onto elevator table 276 by highwayconveyor 330.

In FIG. 5C, elevator 270 is lifting or raising elevator table 276 towardthe top level. In FIG. 5D, elevator table 276 has reached the top level,and movable tray 10 is pushed off of elevator table 276 and onto parkinglevel 28.

In FIG. 5E, when the parking conveyor on parking level 28 moves movabletray 10 against test station 20, retractable connector 14 is extendedfrom well 26 to make contact with motherboard connector 12. Test station20 then applies power to motherboard substrate 30 through retractableconnector 14 and motherboard connector 12, and components 42, 44 areactivated, causing the microprocessor to boot and begin executinginstructions in a boot routine stored in a ROM.

During this boot routine, memory addresses are generated and sent tomemory module 18, which was earlier inserted into test socket 51 by arobotic arm at loader 348 of FIG. 3. The boot routine writes and readsmemory locations in memory module 18 to determine if memory module 18 isfaulty or good. Additional test routines may be activated to moreextensively test memory module 18, or power may be cycled on and off tomotherboard substrate 30 to repeatedly test memory module 18, such asfor burn-in testing.

After testing is complete, results may be detected by test station 20over retractable connector 14 and sent to the host controller overEthernet 24. Test station 20 retracts retractable connector 14 into well26, and movable tray 10 may then be moved along the parking conveyor atparking level 28, carrying motherboard substrate 30 away from teststation 20 toward elevator table 276.

Test station 20 is out of the reach of the robotic arm. Motherboardsubstrate 30 must be carried by movable tray 10 down elevator 270 andalong highway conveyor 330 to return to unloader 344 so that the roboticarm may remove memory module 18 from test socket 51.

FIGS. 6A-C are top views of testing a motherboard in a movable tray at aparking level in the parking and testing structure. In FIG. 6A, movabletray 10 is raised to the level of parking level 28 by elevator table276. Movable tray 10 holds two motherboard substrates 30, each withmemory modules 18 inserted into test sockets.

Movable tray 10 is forced off of elevator table 276 and onto parkinglevel 28, such as by a roller, pushing rod, forklift mechanism, or othermethod. In FIG. 6B, movable tray 10 has moved off of elevator table 276and onto parking level 28. A parking conveyor or other movement deviceforces movable tray 10 to the back of parking level 28 near test station20.

Once movable tray 10 and motherboard substrate 30 are aligned the hostcontroller or parking structure controller may instruct test station 20to extend retractable connector 14 from well 26. Retractable connector14 then makes contact with motherboard connector 12, as shown in FIG.6C. Power and ground connect from test station 20 to motherboardsubstrate 30, causing motherboard substrate 30 to power up and re-bootor otherwise initialize. During booting, the CPU on motherboardsubstrate 30 writes and reads to locations in memory modules 18, thustesting memory module 18. Further test programs may be executed bymotherboard substrate 30 after booting. The results of these tests arereported back to test station 20 through motherboard connector 12 andretractable connector 14, and test station 20 reports the test resultsback to the host controller over Ethernet 24. After testing, retractableconnector 14 is again retracted into well 26, breaking the electricalconnection to motherboard substrate 30.

Test results can be communicated from motherboard substrate 30 to teststation 20 through connectors 12, 14, which may have a serial link,differential lines, or a full Ethernet connection.

FIG. 7 shows the loader-unloader in more detail. A stack ofmanufacturing trays are received from a manufacturing or assembly lineas input tray stack 347. Loader elevator 349 removes one manufacturingtray from input tray stack 347 and exposes the memory modules in thattray to robotic arm 364. Robotic arm 364 removes four memory modulesfrom the manufacturing tray exposed by loader elevator 349 and insertsthese memory modules into SPD programmer 356. SPD programmer 356performs a simple open/shorts D.C. test on these memory modules, andthen programs the SPD-EEPROM on each module with various information,such as the size and configuration of the memory, and an identificationof the memory manufacturer. Memory modules that fail the open/shorttest, or fail to verify after SPD programming are moved by robotic arm364 to reject tray 358. These defective memory modules may be reworked,recycled, or disposed of.

Memory modules that pass the open/shorts test and successfully programare picked up by robotic arm 364 from SPD programmer 356. Two of thememory modules are inserted into two test sockets on one motherboard andthe other two memory modules are inserted into two test sockets onanother motherboard on movable tray 10 by robotic arm 364. Movable tray10 with the loaded motherboards can then be moved by highway conveyor330 to parking and testing structure 350 for testing.

After testing by the motherboards at parking and testing structure 350,movable tray 10 is returned from parking and testing structure 350 byhighway conveyor 330. Robotic arm 364 then removes the memory modulesfrom the test sockets on the motherboards in movable tray 10 and placesthese memory modules into an output tray that is exposed by unloaderelevator 345. Any defective memory modules that failed the motherboardtest are moved by robotic arm 364 to reject tray 358.

Host controller 362 can be a personal computer that controls robotic arm364. Test results from a parking structure PC that controls testing inparking and testing structure 350 can be sent over a local network suchas an Ethernet to host controller 362, which later matches test resultswith memory modules picked up by robotic arm 364 from movable tray 10.Host controller 362 could track movements of all movable trays 10 andstore test results for each tracked movable tray 10.

Once the output tray exposed by unloader elevator 345 is full, unloaderelevator 345 can move the full output tray to output tray stack 343. Astack of output trays can them be removed and sent to shipping.

FIG. 8 shows an alternate embodiment of the parking and testingstructure. In this embodiment, input highway 332 is located one levelabove output highway 334. Each level reached by elevator table 276 inelevator 270 has two parking conveyors 280 in opposite directions.Another alternative is to have four parking conveyors 280 for eachparking level, with two more parking conveyors 280 (not shown)perpendicular to the plane of the drawing page.

Test station 20 is located at the end of each parking conveyor 280, evenat the two levels used by highway conveyor 330.

Many motherboard substrates 30 may be activated in parallel to testmemory modules. For example, when there are 4 test stations 20 perparking level, and 10 parking levels of parking conveyor 280, a total of40 motherboards may be testing memory modules at any particular time ineach parking and testing structure 350. Having two parking and testingstructures 350, 352 can double testing to 80 motherboards. A singlerobotic arm 364 may thus be shared for use with all 80 motherboards,thus reducing the per-unit-tested cost of robotic arm 364.

This is ideal for slower test routines. A large number ofmotherboard-based testers are used, with only a single robotic arm. Thusthe cost of the robotic arm is spread over a large number of inexpensivemotherboards, reducing test costs.

FIG. 9 is an elevator that raises and lowers movable motherboard-basedtesters. Wheels 402 rotate to cause belts 408 to rotate in oppositedirections. The left belt 408 rotates in a counter-clockwise fashion,while the right belt 408 rotates in a clockwise fashion.

Belts 408 have brackets 404 attached to them. Brackets 404 supportelevator tables 406, which are inserted at the bottom and removed at thetop. Movable tray 10 can be moved onto elevator table 406 and liftedinto the desired level before being removed. Table 406 does not need tophysically exist in some embodiments. For example, brackets 404 can beextended to support tray 10. Alternately, table 406 can be made part oftray 10, such as by a side protrusion from tray 10 for insertion intobracket 404.

Since this elevator moves in only one direction, a pair of elevators maybe used. Alternately, wheels 402 may be rotated in a reverse directionto lower movable tray 10 so that the elevator may move in both up anddown directions.

FIG. 10 is a diagram of a Ferris-wheel type of elevator. Wheels 204, 206rotate, causing chain 208 to rotate in a looping fashion. Chain 208 hasseveral baskets 202 attached to it that can swing freely. Each basket202 can hold one movable tray 10 with a motherboard substrate 30 in it.

When a basket 202 reaches the end of input conveyor 284, a movable tray10 may be moved from input conveyor 284 onto basket 202. A loaded basked202 may be unloaded when reaching one of conveyor belts 280, 281, 282.Empty baskets 202′ are then returned to be reloaded from input conveyor284. Wheels 204, 206 may be paused to allow loading and unloading ofbaskets 202. Activated-rods may be used to push movable tray 10 on andoff of baskets 202. A forklift-type mechanism may be used as well.

Alternate Embodiments

Several other embodiments are contemplated by the inventors. Whileconveyor belts have been described, conveyors may not use belts, but mayuse rollers, escalators, or other type of conveying apparatus for movingobjects. Elevator 270 could be a single elevator with a larger elevatortable that could hold two movable trays 10 at a time. Hydraulics couldbe used to raise or lower the elevator table, or a cable or chain drivenby a motor as in a conventional elevator. A solenoid, gears, or othermechanism may be used to move retractable connector 14.

While a retractable connector has been described, retractable connector14 could be fixed in place, and the motherboard connector pressed intothe retractable connector when movable tray 10 and the motherboard aremoved to the end of the parking conveyor. More than one test station 20could be located per parking level, and the parking conveyor or highwayconveyor could have junctions, diverters, joints, etc.

Movable tray 10 could hold only 1 motherboard, or could hold more than 1motherboard. Different sizes and form factors of the motherboards couldbe supported by movable tray 10. Also, movable tray 10 could befixatedly attached to the motherboard or could be integrated with themotherboard, or the motherboard could be freely positioned in movabletray 10. The motherboard might have a tray attached to it, or a carrierof some sort that prevents the motherboard from shoring to any metallicparts of the conveyor system. Movable tray 10 can be made from aninsulating material to prevent shorting of the motherboard to theconveyor. The conveyor system can be a standard conveyor such as usedfor moving boxes or other items, or may be more specialized. Suchconveyer systems may include turns, bends, rotates, branching, lifts,etc.

Buffers can be added at various locations, such as on highway conveyor330. Buffers can be implemented as additional conveyors that can hold avariable number of motherboards. The elevator wait delay may be reducedusing buffers or other queues.

Additional buffers, rotators, elevators, or other components could beadded at various locations. The number of levels in a conveyor stack mayvary, and the number of parallel conveyor stacks may also vary. Whiletesting memory modules has been described, other components could betested as the MUT. Hot or cold air could be applied to the MUT while themotherboard is stationary at test station 20. MUT's could also bepre-heated at an earlier station on the conveyor.

Input highway 332 and output highway 334 could be connected to theelevators at any level, rather than at the lowest level. Connection to amiddle level could reduce elevator delay.

Multiple highway conveyors 330 could be used, perhaps with multipleloading and unloading stations. Rather than have a single robotic arm,two or more robotic arms could be used. Each robotic arm could pick andplace one or more memory modules.

Local heaters could be mounted on the motherboard substrate or on teststation 20. Radiant heat sources could be used or a resistive element.Radiant elements could directly heat the memory module.

Many kinds of memory modules can be tested. Modules using standard DRAMor newer EDO and synchronous DRAM can be tested. The system is ideallysuited for testing the highest-speed memory modules, since capacitiveloading is minimized. Other memories such as RAMBUS modules, DDRmodules, and PC133 synchronous modules can be tested. Other kinds ofelectronic devices could be tested, such as SD memory cards, USB flashdrives, and solid-state hard drives. Testers are not limited tomotherboard-based testers, but may include other kinds of testers thatcan be placed on a conveyor.

Various sizes of memory in the memory module, and form factors formemory modules can be used with the invention, limited by the testadaptor board and well size. Different kinds of test adaptor boards canbe substituted. The reverse-mounting of the test adaptor boards and thesolder-side up arrangement of the test station allows a technician oroperator to easily replace the test adaptor boards when necessary. Thetest adapter board can also be mounted to the motherboard in asubstantially perpendicular orientation. See for example, U.S. patentapplication Ser. No. 10/249,841, “Robotic Memory-Module Tester UsingAdapter Cards for Vertically Mounting PC Motherboards”, now U.S. Pat.No. 7,509,532. Non-PC motherboards can also be used. The invention canbe applied to any target system board. Multiple test sockets can bemounted on each test adapter board, or multiple test adapter boards maybe mounted on a single motherboard, allowing multiple memory modules tobe tested at the same time by the same motherboard acting as a tester.

While FIGS. 5, 6, 9 show the component side of motherboard substrate 30facing upward, the component side could face downward in movable trays10, allowing a test adaptor board mounted to the solder-side of themotherboard to face upward. This arrangement may assist the robotic armin reaching the test sockets on the test adaptor board. An extender cardcould be used to raise the level of the test sockets with or without atest adaptor board.

A Yamaichi type connector could be used as the test socket, asmotherboard connector 12, or as retractable connector 14. Aproduction-quality connector/socket is preferred due to the lowinsertion force required. A production quality connector/socket can takemore insertions (greater than 100,000 times) than conventional socketson motherboards (rated for 100 insertions). A production socket may alsohave an ejector normally located at the edges of the socket. Thisalleviates the ejection of modules for manual as well as robotichandling. A production socket may also contain a V-shape groove. Ahandler or a robotic arm can drop the module to the V-shape entry, letit settle, and then push the module from the top to the socket. The Vshape entry can lower the accuracy requirement to the handler or roboticarm for insertion of the module. Motherboard connector 12 andretractable connector 14 could also employ self-alignment orpositioners.

A variety of technologies can be used for the robotic arm. A swinging orpivoting arm can be used, with perhaps a telescoping arm extension and avertical servo at the end of the arm. Alternately, an x-y-z track systemcan be used. Many variations of automatic tray stacker or elevatorsystems are known and can be employed. The test program can initiallypause after insertion of a new memory module to allow it to be warmed upby hot air. Memory modules could also be pre-heated by blowing hot aironto modules waiting to be inserted and tested. The input tray could beheated to accomplish this.

Many kinds of robotic arms and tracking systems can be employed, withdifferent degrees of motion. Different grasping technologies can be usedto hold the memory modules in the robotic arm. Multiple robotic armsthat operate in tandem or independently can be used with the loader andunloader. For example, one arm can load modules into the motherboards,while a second arm unloads tested modules.

While separate loader and unloaders have been described, a singleloading station could be substituted. The movable tray could remainstationary at the loading station for both unloading and loading.Alternately, the movable tray could be unloaded at one position, thenmoved to another position for loading as described in FIG. 3. The termloader-unloader includes both separate loading and unloading positions,and a unified loading and unloading position.

One operator may be able to operate several test stations, depending onhow quickly trays need to be inserted and removed. Multiple arms can beattached to robot arm assembly 364, allowing 2 or more memory modules tobe picked up and moved at the same time. The test adaptor boards can bemodified to have two or more test sockets, allowing two or more modulesto be tested at the same time with the same motherboard. The motherboardcan then report which of the 2 modules has failed to the host controlleror main system interface.

A network controller card on the ISA or PCI bus that communicates withthe main system interface (host controller 362) can be adapted for otherbuses and is not limited to existing buses. The controller card can bereplaced by a standard parallel or serial-port interface to the mainsystem interface. FireWire, USB, Ethernet, or other emerging standardscan be used for the interfaces.

Cold air rather than hot air could be blown onto the memory module. Thismight be useful for characterizing modules rather than for guard-bandtesting. Humid hot air could be used for testing hermetic seals ofmemory chips on the memory module, and even hot and cold air cyclingcould be done for reliability testing. The air may be recycled andre-blown through the channel by a blower or other air-flow system.

The test results could be stored in a non-volatile memory on themotherboards, such as in a battery-backed memory or anelectrically-erasable programmable read-only memory, EEPROM, or in theSPD memory on the memory module. Then unloader 344 would power up themotherboard or memory module to read the test results. An SPD readernear unloader 344 can also be used to read the test results.

The background of the invention section may contain backgroundinformation about the problem or environment of the invention ratherthan describe prior art by others. Thus inclusion of material in thebackground section is not an admission of prior art by the Applicant.

Any methods or processes described herein are machine-implemented orcomputer-implemented and are intended to be performed by machine,computer, or other device and are not intended to be performed solely byhumans without such machine assistance. Tangible results generated mayinclude reports or other machine-generated displays on display devicessuch as computer monitors, projection devices, audio-generating devices,and related media devices, and may include hardcopy printouts that arealso machine-generated. Computer control of other machines is anothertangible result.

Any advantages and benefits described may not apply to all embodimentsof the invention. When the word “means” is recited in a claim element,Applicant intends for the claim element to fall under 35 USC Sect. 112,paragraph 6. Often a label of one or more words precedes the word“means”. The word or words preceding the word “means” is a labelintended to ease referencing of claim elements and is not intended toconvey a structural limitation. Such means-plus-function claims areintended to cover not only the structures described herein forperforming the function and their structural equivalents, but alsoequivalent structures. For example, although a nail and a screw havedifferent structures, they are equivalent structures since they bothperform the function of fastening. Claims that do not use the word“means” are not intended to fall under 35 USC Sect. 112, paragraph 6.Signals are typically electronic signals, but may be optical signalssuch as can be carried over a fiber optic line.

The foregoing description of the embodiments of the invention has beenpresented for the purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed. Many modifications and variations are possible in light ofthe above teaching. It is intended that the scope of the invention belimited not by this detailed description, but rather by the claimsappended hereto.

We claim:
 1. A multi-level test system for testing electronic devices onmovable electronic testers comprising: a plurality of electronictesters; test sockets on the plurality of electronic testers, the testsockets for receiving electronic devices for testing; a loader-unloaderfor inserting electronic devices into test sockets on electronic testersin the plurality of electronic testers when the electronic testers areat a loading station; a parking-testing structure having a plurality ofparking levels, each parking level for temporarily holding an electronictester in the plurality of electronic testers during testing of theelectronic devices in the test sockets; a plurality of test stations,for connecting to electronic testers in the plurality of electronictesters and for activating the electronic testers to test the electronicdevices inserted into the test sockets on the electronic testers;wherein each parking level in the plurality of parking levels has a teststation in the plurality of test stations that connects to an electronictester in the plurality of electronic testers that is currently parkedon each parking level; a conveyor for moving the plurality of electronictesters from the loading station to the parking-testing structure, andfor moving the plurality of electronic testers from the parking-testingstructure to the loading station after testing by the plurality of teststations, whereby the electronic devices are inserted into electronictesters that are moved by the conveyor to the parking-testing structurefor testing, and wherein the conveyor moves electronic testers back tothe loading station after testing.
 2. The multi-level test system ofclaim 1 further comprising: movable trays that are placed on theconveyor, each movable tray for holding an electronic tester in theplurality of electronic testers, each movable tray moving along theconveyor to transport the electronic tester from the loading station tothe parking-testing structure, and to return the electronic tester tothe loading station after testing.
 3. The multi-level test system ofclaim 2 wherein the movable trays electrically insulate the plurality ofelectronic testers from the conveyor during testing by the plurality oftest stations.
 4. The multi-level test system of claim 1 furthercomprising: test adaptor boards, each coupled to an electronic tester inthe plurality of electronic testers, the test adaptor boards having thetest sockets for receiving electronic devices for testing by theelectronic testers, each test adaptor board for electrically connectingan electronic device inserted into a test socket to an electronic testerattached to the test adaptor board.
 5. The multi-level test system ofclaim 4 wherein circuit boards of the electronic testers have acomponent side and a solder side, the component side having integratedcircuits mounted thereon; wherein the test adaptor boards are mounted tothe solder side of circuit boards of the electronic testers.
 6. Themulti-level test system of claim 1 further comprising a parkingstructure system interface, coupled to the plurality of test stations inthe parking-testing structure, for commanding test stations in theplurality of test stations to apply power to activate electronic testersto test electronic devices inserted into the test sockets and forreceiving test results from the electronic testers; a main systeminterface for controlling the loader-unloader to sort electronic devicesbased on the test results; a network between the parking structuresystem interface and the main system interface, for communicating thetest results from the parking-testing structure to the loader-unloader;wherein the main system interface stores the test results while theelectronic tester is being returned from the test station to theloader-unloader after testing by the test station.
 7. The multi-leveltest system of claim 6 wherein the loader-unloader further comprises: arobotic arm, responsive to commands from the main system interface, forinserting electronic devices into the test sockets on electronictesters.
 8. The multi-level test system of claim 1 wherein theparking-testing structure further comprises: an elevator for raising andlowering an electronic tester to the plurality of parking levels of theparking-testing structure; and an input level of the elevator, the inputlevel coupled to the conveyor between the loading station and theelevator.
 9. The multi-level test system of claim 8 wherein the conveyorfurther comprises: an input conveyor line between the loading stationand the elevator; an output conveyor line between the elevator and theloading station.
 10. The multi-level test system of claim 9 wherein theinput conveyor line and the output conveyor line are coupled to theelevator at different levels of the elevator, whereby the input conveyorline and the output conveyor line are on two different levels.
 11. Themulti-level test system of claim 9 further comprising a plurality ofparking conveyors on the plurality of parking levels of theparking-testing structure, a parking conveyor for moving an electronictester from the elevator to the test station before testing, and formoving the electronic tester from the test station to the elevator aftertesting.
 12. The multi-level test system of claim 2 wherein each teststation in the plurality of test stations further comprises: aretractable connector for extending to make electrical contact with anelectronic tester connector on an electronic tester.
 13. Amoving-electronic-tester electronic-device tester comprising: aplurality of electronic testers, an electronic tester in the pluralityof electronic testers for executing a test program to test an electronicdevice inserted into a test socket on the electronic tester; aDevice-Under-Test (DUT) loader-unloader having a robotic device thatremoves a tested electronic device from the test socket on theelectronic tester, and that inserts an electronic device into the testsocket on the electronic tester when the electronic tester is located atthe DUT loader-unloader; an input highway that moves the electronictester away from the DUT loader-unloader after the electronic device hasbeen inserted into the test socket; an output highway that moves theelectronic tester toward the DUT loader-unloader after the electronicdevice in the electronic tester has been tested; an elevator thatreceives the electronic tester from the input highway, and that returnselectronic testers to the output highway, the elevator raising andlowering the electronic testers to a plurality of parking levels; aparking-testing structure having the plurality of parking levelsaccessible by the elevator, each parking level having a testing conveyorthat receives electronic testers from the elevator; a plurality of teststations in the parking-testing structure, each test station on aparking level having a parking connector that connects to an electronictester connector on the electronic tester when parked at the parkinglevel, the parking connector applying power to the electronic tester toactivate the electronic tester to test the electronic device in the testsocket; and a network connection to the plurality of test stations forcommunicating test results from the plurality of test stations testingthe plurality of electronic testers, wherein the test results controlthe DUT loader-unloader to sort electronic devices when the roboticdevice removes the tested electronic devices, wherein test resultsindicating that the electronic device failed testing are sorted into afailed group of electronic devices while test results indicating thatthe electronic device passed testing are sorted into a passing group ofelectronic devices by the robotic device, whereby electronic devices aretransported from the DUT loader-unloader to the plurality of teststations by the input highway, the elevator, the testing conveyor, andthe output highway that move the plurality of electronic testers betweentest stations and the DUT loader-unloader.
 14. Themoving-electronic-tester electronic-device tester of claim 13 furthercomprising: a plurality of movable trays that carry the plurality ofelectronic testers along the input highway, the elevator, the testingconveyor, and the output highway, whereby electronic testers are carriedby the plurality of movable trays.
 15. The moving-electronic-testerelectronic-device tester of claim 14 further comprising: a test adaptorboard mounted to each electronic tester, wherein the test socket ismounted on the test adaptor board, the test socket for receiving anelectronic device inserted by the robotic device.
 16. Themoving-electronic-tester electronic-device tester of claim 14 whereinthe parking-testing structure comprises at least 5 parking levels and atleast 10 test stations, wherein the parking-testing structure tests atleast 10 electronic testers in parallel.
 17. Themoving-electronic-tester electronic-device tester of claim 16 whereinthe plurality of parking levels in the parking-testing structure arelocated vertically above each other, whereby floor space is minimized.18. The moving-electronic-tester electronic-device tester of claim 13wherein each test station further comprises: a test-station connectorthat makes electrical contact with an electronic tester connector on theelectronic tester; wherein power is applied through the test-stationconnector and the electronic tester connector by the test station whentesting the electronic device on the electronic tester.
 19. Amultiple-electronic-tester parking-testing structure electronic testercomprising: host system means for controlling testing of electronicdevices on multiple electronic testers and for controlling movement ofelectronic testers by conveyors; test socket means for receiving anelectronic device for testing; conveyed electronic tester means,controlled by the host system means, for executing a test program on anelectronic device inserted into the test socket means; wherein themultiple-electronic-tester parking-testing structure electronic testerhas a plurality of the conveyed electronic tester means, each conveyedelectronic tester means for executing the test program on a differentelectronic device in parallel with other electronic tester means;robotic means, controlled by the host system means, for grasping anelectronic device and inserting the electronic device into the testsocket means, the robotic means also for grasping and removing theelectronic device from the test socket means after completion of thetest program, and moving the electronic device to an output means forstoring tested electronic devices when the conveyed electronic testermeans indicates to the host system means that the electronic device haspassed the test program; test station means for applying power to theconveyed electronic tester means to activate the conveyed electronictester means to test the electronic device inserted into the test socketmeans; parking-testing structure means for parking a plurality of theconveyed electronic tester means on a plurality of parking levels, eachparking level having at least one test stations means, wherein theplurality of parking levels overlap each other to occupy a same floorspace; wherein the plurality of parking levels and the test stationmeans are not accessible by the robotic means; elevator means forraising and lowering the conveyed electronic tester means on an elevatortable to the plurality of parking levels in the parking-testingstructure means; and conveying highway means, coupled between theelevator means and a loading station that is accessible by the roboticmeans, for moving the conveyed electronic tester means from the loadingstation to the elevator means before testing, and for moving theconveyed electronic tester means from the elevator means to the loadingstation after testing, whereby electronic testers are moved from theloading station to a parking level in the parking-testing structuremeans before testing, and moved from the parking-testing structure meansback to the loading station after testing.
 20. Themultiple-electronic-tester parking-testing structure electronic testerof claim 19 further comprising: tray means for holding the conveyedelectronic tester means during transport between the loading station andthe test station means.